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Date:      Sat, 21 Feb 2009 13:17:33 +1030
From:      "Daniel O'Connor" <doconnor@gsoft.com.au>
To:        freebsd-current@freebsd.org
Cc:        David Christensen <davidch@broadcom.com>
Subject:   Re: Hopefully Simple Question on Debugging Kernel Modules
Message-ID:  <200902211317.41479.doconnor@gsoft.com.au>
In-Reply-To: <5D267A3F22FD854F8F48B3D2B5238193394588D54D@IRVEXCHCCR01.corp.ad.broadcom.com>
References:  <5D267A3F22FD854F8F48B3D2B5238193394588D54D@IRVEXCHCCR01.corp.ad.broadcom.com>

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On Saturday 21 February 2009 10:10:56 David Christensen wrote:
> I'm sure this is a simple question but the answer is alluding my Google
                                                 eluding -^

> search capabilities.  My driver is being loaded as a kernel module and
> is failing with the following error:
>
> Fatal trap 12: page fault while in kernel mode
> cpuid =3D 0; apic id =3D 00
> fault virtual address   =3D 0xfffffffe40abe9dc
> fault code              =3D supervisor write data, page not present
> instruction pointer     =3D 0x8:0xffffffff920b638f
> stack pointer           =3D 0x10:0xffffffff9212bb10
> frame pointer           =3D 0x10:0xffffffff9212bbb0
> code segment            =3D base 0x0, limit 0xfffff, type 0x1b
>                         =3D DPL 0, pres 1, long 1, def32 0, gran 1
> processor eflags        =3D interrupt enabled, resume, IOPL =3D 0
> current process         =3D 12 (irq268: bce0)
> [thread pid 12 tid 100166 ]
> Stopped at      bce_intr+0x8df: addl    $0x1,0x2c854(%r12,%rax,4)
> db>
>
> I simply need to find the offending source line in my driver.  Not sure
> how I've managed to get the driver running at all without this but it's
> time to do things the right way.  I have KDB/DDB/GDB built into my
> -CURRENT kernel already.  It'd be great to find the source line while in
> the kernel debugger but I'm also fine with rebooting the system to
> identify the line number.

DDB doesn't understand debugging symbols to that degree, however you could=
=20
connect a GDB remotely using a serial or firewire connection (the later is=
=20
much, much nicer)

I imagine you could get GDB or some other tool to tell you what line that=20
offset corresponds to but I'm not sure how you go about doing that with=20
modules loaded unless you have a crash dump (or remote GDB on a live system)

I guess you could also rebuild your .c files with.. -Wa,-adhlmsn=3D$foo.lst=
 and=20
look it up that way.

=2D-=20
Daniel O'Connor software and network engineer
for Genesis Software - http://www.gsoft.com.au
"The nice thing about standards is that there
are so many of them to choose from."
  -- Andrew Tanenbaum
GPG Fingerprint - 5596 B766 97C0 0E94 4347 295E E593 DC20 7B3F CE8C


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